Add missing docs and directives related to PEP 3147 and byte-compilation
diff --git a/Doc/library/runpy.rst b/Doc/library/runpy.rst
index 896b65d..10e5ebc 100644
--- a/Doc/library/runpy.rst
+++ b/Doc/library/runpy.rst
@@ -70,6 +70,9 @@
    .. versionchanged:: 3.1
       Added ability to execute packages by looking for a ``__main__`` submodule.
 
+   .. versionchanged:: 3.2
+      Added ``__cached__`` global variable (see :PEP:`3147`).
+
 
 .. function:: run_path(file_path, init_globals=None, run_name=None)